Thermostatic element



April 13, 1954 v. G. VAUGHAN 2,675,267

r'IHmaoSTATIc ELEMENT' Filed arch 29, 1952 ml/Ewan.

V'gfar 6.' Vaughan?,

Patented Apr. 132 1954 UNIT-so stares PATENT clerics THEBM.QSSIA'IIGA.ELEMENT 'Victor G; Vaughan, Attleboro, Massi, .assigner to Metals &rControls Corporation', Attleboro, Mass., a. corporation of MassachusettsAppliootionlllaroh ,29, 195.2, Serial No. 279,474.1.

`part ofthe device may be `acourately controlled.

nevertheless the .ears .of the device .retain their creep motionAo.haraoteristi.e `o1? rtheruiosiat metal strips. This being the case,when such a device is mounted in .a base` for use `as a movable part .ofan electric switch, itis `soinetimes diflicult to adjust the deviceaccurately as to `operating snap temperaturebecause ofthe creep `rnotion.of the ears or tabs` as thethermostat. isheated.

It is Athe general objectof this nventiontherefore, to provide aconstruction of'such an eared element in which the creep .motion oftheearsis substantially eliminated, thusrurnishing such an inherentlySnape-acting device which .caribe accurately adjusted .to Operate Wtha,snap motion and without any creep .opening being induced'by the actionof the ears.

Among the objects of the invention, therefore, may be noted theprovisionof a snap-acting thermostatic element having ears extendingtherefrom integral with the plate but in which said ears arecompensatedso as substantially toeliminate creep. motion of .the ears; theprovision of a. snap-acting thermostatio element in which the `cars ofthe Ielementare compensated against creep motion by the addition thereonof oppositely moving thermostatic metal; and the provision of. asnap-acting thermostatic element which is 1 isa plan View of .a sheet ofblmetal showing. in dotted lines .how one embodiment of this inventionmay be blanked out of sheet stock Ain an initial stage of'itsmanufacture;

Fig. i2 iS a perspective view of a thermostatic element blankedlout asindicated in Fig. 1;

Fis. .3 shows the blank o f'Fig. 1 after a bending operation has beenperformed .thereon and after the element lhas beendishedforrSnap-action,temperature response;

.Fia 4 is .a cross section. of the Fie. 3 embodiment, taken alone.thesiehtlne 4 4;

Fig. 5 shows a plan view of another embodiment of this invention;

Fie. 6 is. a .cross sectional view .of the Fis. 5` embodiment taken inl.the direction of `sieht line Fig. 7 is .a perspective view of the Fis.5 embodiment .showing electrical contacts mounted thereon;

"Fis- 8 .is a cross. `.section of.' a portion of the ris- 7 embodiment.serving better to illustrate the relationship between componentsthereof; and

Fig. y9 is a view similar toFig.. 8 showing a dif- `ierent arrangementof the components of the Figi? embodiment.

irornsheet I. ASuch*material is Well knownin the agit` and comprises asheet ofmetal having a relatively high coefficient of expansion rrnlybonded to `a sheet ofmetal having a relatively low coemcent` nofexpansion. The resulting thermostatic element `2` is more clearlyillustrated in Fig. 2 and comprises two sheet Aof metal 3 and il firmlybonded together as is customary in the art t of manufaolfurjing`thermostat metal. In this instance, the metal 3 r,is the `-10W expansionmetal and-the -metal c is the high expansion metal. The thermostat'elementi in this instance corn- `prises the disc-like portion 5 havingintegrally attached thereto the earsgindicated generallyby numeral. As`indicatedtjin '3, ,a portion 'l of Veach of ears 'S'is bent back, onthe vremaining portion 1 is welded, as indicatecl'jhy the Weld pointsI0, at several places in order to attach said will be observed that thetwo high expansion layers Il of portions I and 9. are lying adjacenteach other and the two low expansion layers 3 of portions 'I and 9 areon the outside.v When this device is now heated, with the high expansionand low expansion metals arranged as i shown, there will be no tendencyfor either ear itself (independently of disc portion 5) to bend up ordown, since any tendency of portion S to move in one direction will becounteracted by the tendency of portion I to move in the oppositedirection. Thus there is no motion of the ears of the element other thanthat imparted to them when the dished central portion 5 snaps from oneposition of concavity to its other position of concavity.

Preferably after the portions 'I are welded to portions 9, the centralpart 5 of the device is dished to provide a non-developable surface suchas will snap back and forth in response to temperature changes, asdescribed in United States Patent 1,448,240.

Fig. 4 illustrates more clearly, by the cross sectional showing, therelationship of parts of the Fig. 3 snap-acting device, showing the twohigh expansion layers 4 adjacent each other and the low expansion layers3 on the outside.

Referring noW to Figs. 5 and 6, there are shown, respectively, plan andcross-sectional side vievv's'of another embodiment of the invention inwhich the additional compensating Apieces of thermostat metal I2 and I2are not initially blanked as anY integral part of the thermostat elementas a whole, but are separate pieces of thermostat metal Welded to theeared portions I3 and I3 of the thermal element and serving exactly asbefore to compensate for anyundesired motion of the ears I3 and I3.V Inthis case,

Vthe thermostat metal pieces I2 are shaped to match the outline of theeared portions I3 `to which they are to be attached, andthen theportions I2 are attached in place as by welding.

Preferably, these additional pieces I2 are made from metalfhaving thesame characteristics as Vthe metal the main element is madefrom. Invthis case, as in the Figs. 1-4 embodiment, the

relationship .of the high expansion and low expansion sides of therespective thermostat metals is so arranged that any tendency of eachvof the ears I3 to move in one direction is counteracted by oppositetendency of the added piece I2. Again, in this embodiment, the two higheXpansion metals 4 and 4 are adjacent and the two low expansion metals 3and 3 are on the outside.,

Referring now to Fig."7, there is shown'aper; spective view of the discof Fig. 6 to which have been attached as by welding or soldering, theelectrical contacts I4 and I4. The positioning of the thermostat metalpieces I2 and I2 is clearly vshown in this drawing.

In Fig. 8 there is shown a cross section of one eared-portion of theFig. '7 device, to show more clearly the relationship of parts, with thetwo low expansion metals 3 and Sonthe outside, and the two highexpansion meta1s4 and d adjacent to each other.

Vcent to eachother.

In Fig. 9 a view similar to Fig. 8 is given, but in this instance itwill be noted that the additional pieces of metal I2 are fastened to theother side of the ears I3 of the element. Thus, in this Fig. 9arrangement the two high expansion sides 4 of thermostat metal are onthe outside and the two low expansion sides 3 are adja- Again, asbefore, any tendency of ear I3 to move in one direction withternperature change is counteracted by an equal and Opposite tendency onthe part of piece I2.

. equally well apply to the Fig. 3 embodiment.

This same Fig. 9 arrangement of parts can In such a case, the portions'I of the device would have been bent on the bend lines 8 to lie on theother side of the ear portions 3 rather than onthe side shown in Fig. 3.It is to be clearly observed that if such positioning had been done,then (as in Fig. 9), the two low expansion metals would be adjacent toeach other and the two high a expansion metals would be the outerlayers.

In respect to all of the embodiments, the ends I5 of ear portions I andthe inner ends I9 of ear portions I2 are preferably curved so that whenvthese compensating portions are fastened in place r,the curvature issuch as to follow the projected .Y curvature of the perimeter of centralportion 5.

In View of the above, it willv be seen that the several objects of theinvention are achieved and other advantageous results attained. As manyI changes could be made in carrying out the above constructions withoutdepartingfrom the scope 'of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted Vas illustrative and not in a limitingsense.

I claim:

l. A snap-acting thermostatic element comprising a composite thermostatmetal sheet part having a non-developable surface adapted to change itsshape suddenly upon reaching a predetermined temperature; ears ofcomposite thermostat sheet metal attached to the periphery of said sheetpart; `metal parts overlying said ears and fastened and compositethermostatic thereto immovably with respect to said ears; the directionof unrestrained bending, in response to temperature change, of saidparts being opposite to the direction of unrestrained bending, inresponse to the same temperature change, of said ears.

given temperature change being opposite to the direction of unrestrainedcreep motionY of said ears for the same temperature change.

3. Asnap-acting thermostatic element comprising a composite thermostatmetal sheet part having a nondevelopable surface adapted to change itsshape suddenly upon reaching a predetermined temperature; first ears ofcomposite thermostat sheet metal attached to the periphery of said sheetpartV as an integral part thereof; and second ears of compositethermostat sheet metal overlying said` rst ears and `attached theretoimmovably with respect to said rst ears,

annee? the high expansion metal component of each of said second earslying adjacent to the high expansion metal component of its respectiverst ear.

4. A snap-acting thermostatic element comprising a composite thermostatmetal sheet part having a nonedeveiopable surface adapted to change itsshape suddenly upon reaching a predetermined temperature; rst ears ofcomposite thermostat sheet metal attached to the periphery of said sheetpart as an integral part thereof; and second ears of compositethermostat sheet metal overlying said first ears and attached theretoimmovably with respect to said first ears, the 10W expansion metalcomponent of each of said second ears lying adjacent to the lowexpansion metal component of its respective irst ear.

5. An inherently snap-acting thermostatic element comprising a centraldisc-like portion having a non-developable surface adapted to change itsshape suddenly upon reaching a pre-determined temperature; two firstears formed as integral parts of said central portion and extending fromthe rim thereof at opposite ends of a diameter; and second ears ofcomposite thermostat metal overlying said first ears and attachedthereto immovably with respect to said first ears to counteract anycreep-motion of said iirst ears, the direction of motion of said secondears for a given temperature change being opposite the direction ofmotion of said rst ears for the same temperature change.

6. The disc of claim 5, in which said second ears are integralextensions of said rst ears, said extensions being folded back ove1`said rst ears to lie adjacent thereto.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,317,831 Vaughan Apr. 27, 1943 2,487,684 Smith Nov. 8, 19492,533,274 Matulaitis Dec. 12, 1950

